Some side-impact air bag modules are currently secured to an internal frame of a vehicle seat and are concealed within the seat by the seat cover. Upon being deployed, the air bag is supposed to expand through a frangible seam in the seat cover at a predetermined location to protect the occupant's head and torso at the event of a side impact sufficient to cause deployment. The timing of air bag deployment in the event of crash conditions is critical in terms of providing the maximum safety benefit thereby, and delays in deployment even on the order of fractions of a second can impair the safety functioning of the air bag. Where the air bag is contained within a seat, it therefore must not experience delays in the time from firing of the air bag to the time the air bag breaks through the intended seam of rupture. However, seat covers are usually of a stretchable material, and in some instances, it has been found that rather than having a proper and timely break through the seam, the air bag will start to inflate the stretchable seat cover prior to emerging from the seam thus delaying the desired time of rupture and bag inflation exterior of the seat. Accordingly, a more predictable path of deployment for an air bag that deploys from within a seat and through an intended seam of rupture is needed to obtain maximum safety benefits with the bag.
Sometimes a new special frangible seam is provided in the seat cover adjacent a bolster seam in the upholstery seat cover material through which the air bag is to be deployed. It is usually preferred that the air bag module be mounted in the seat so that its location is invisible to the seat occupant; and, to this end, the air bag is preferably deployed through a conventional bolster seam joining together adjacent, vertical edges of adjacent panels of the seat cover. If a new deployment seam is used, it is often located near the bolster seam to allow the air bag to deploy at an angle which is not possible with the use of the existing bolster seam. The use of a special seam for air bag deployment detracts from the appearance of the seat and adds additional cost and time to manufacture the seat having an air bag module hidden therein.
To ensure that the air bag properly deploys in a predictable or repeatable path to protect the seat passenger, a chute of fabric material has been wrapped about the air bag module and is fastened to the back of the air bag module by a zipper or threaded fastener. The fastening of the chute behind the air bag is difficult; and, in some instances, so difficult that it has caused the seat manufacturer to use a separate hard plastic panel at the back of the seat rather than the usual upholstery cover fabric at the back of the seat. The hard plastic back panel adds weight and cost to the seat.
Another suggested approach to guide the air bag to deploy through a frangible upholstery seam involves the use of a rigid plastic sheet attached to the foam seat pad and having a slit in the plastic sheet through which the rigid expanding air bag will proceed. The use of the chute or the hard plastic sheet on the foam pad may result in sink marks in the seat deployment seam when the fabric is pulled tight and stitched together. This is especially true where the chute is connected or integral with the seat upholstery material stitched together to form the seam. The appearance of the seam and seat cover are very important and any such air bag sinks or location marks in the fabric are undesirable.
Thus, it will be seen that these chute systems are costly in terms of manufacturing due to the added complexity of the chute and the labor to properly install the chute and air bag module, particularly where the chute fastening is difficult and where it has led to the use of a more costly, hard plastic back seat panel, as above described. Moreover, if a special new seam is required to deploy the air bag at a particular angle, this results in a variety of seat covers each being specific to certain vehicle or vehicle location. Thus, there is a need to eliminate the chute, and/or the special deployment seam in the seat cover, upholstery material.